On my (amateur) level of reading about the selection of the F-35 it seems that the VTOL was a requirement put in by the Marines so that they wouldn't always hav

On my (amateur) level of reading about the selection of the F-35 it seems that the VTOL was a requirement put in by the Marines so that they wouldn't always have to rely on the Navy for operations. This is a tradition that goes back to the WWII and Guadalcanal, where some felt they could never again rely on another arm of service (long story). Others in the Marines basically feel that there mission is different enough to justify their smaller Wasp amphibious carriers (which require VTOL). So what you have then are two contradictory requirements (which those in software will recognize as common when coming from above): (1) Make a single common airframe that serves the Airforce, Navy and Marines. (2) Make that airframe fit the particular requirements of each arm of the services. The F-35 is relatively wide-bodied to accommodate the lift fan on the F-35B (the VTOL variant). This means that weight and size then impact the Airforce and Navy variants (the F-35A and C). The Airforce get a slow, heavy fighter, the Navy get a thirsty lower-ranged aircraft and the Marines get a more expensive and fragile VTOL, but at the expense of everyone else.